Insect Evolution

Hexapoda Insecta Pterygota Neoptera Holometabola Apterygotes 500 400 300 200 100 0 Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Entognatha Archaeognatha Hexapoda Zygentoma Ephemeroptera Insecta Odonata Plecoptera Embiodea Pterygota Zoraptera Dermaptera Grylloblattodea ? Mantophasmatodea Orthoptera Phasmatodea Blattaria Isoptera Mantodea Neoptera Psocoptera Phthiraptera Thysanoptera Hemiptera Coleoptera Rhaphidioptera Megaloptera Neuroptera Hymenoptera Holometabola Mecoptera Siphonaptera Diptera Apterygotes Strepsiptera Trichoptera Paleoptera Lepidoptera Hemimetabolous Holometabolous

Relationships among Hexapoda Collembola Entognatha Protura Diplura Hexapoda Archaeognatha Insecta Thysanura Pterygota

Evolution of the Insects (Carpenter - 1953) Four stages in insect evolution 4. Development of metamorphosis 3. Development of wing flexion mechanisms 2. Development of wings 1. Appearance of primitive wingless insects

Stages of Insect Evolution (Carpenter, 1953) 1. Apterygotes First insect fossils First terrestrial arthropod fossils First terrestrial arthropod trace fossils

Trace Fossils

Hexapoda Characteristics 1) Fusion of second maxillae 1st maxilla 2nd maxilla 2) Fixation of abdominal segments at 11 3) Loss of jointed abdominal appendages

Stages of Insect Evolution (Carpenter, 1953) 1. Apterygotes on Land Devonohexapodus - marine hexapod from the Devonian

Stages of Insect Evolution (Carpenter, 1953) 2. Development of wings a. From what structural elements are wings composed? b. For what purpose were wing-like structures first used? 2. Development of wings

Stages of Insect Evolution (Carpenter, 1953) 2. Development of wings 1. Paranotal Theory paranotal lobes Paleodictyoptera

Stages of Insect Evolution (Carpenter, 1953) 2. Development of wings 1. Paranotal Theory venation lobes

Stages of Insect Evolution (Carpenter, 1953) 2. Development of wings 2. Gill Theory

Stages of Insect Evolution (Carpenter, 1953) 2. Development of wings 2. Gill Theory

Stages of Insect Evolution (Carpenter, 1953) 2. Development of wings 2. Gill Theory Pros –genes in crustaceans for basal legs are homologous with genes for wing development Cons – skimming (Marsden) – rare in primitive pterygotes - most insect ancestors are terrestrial - aquatic insects appear 100 my after wings - genetic evidence – weak since wings are polygenic - Carboniferous insects – big wings but no fossilized aquatic nymphs

Hexapoda Insecta Pterygota Neoptera Holometabola 500 400 300 200 100 0 500 400 300 200 100 0 Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Entognatha Archaeognatha Hexapoda Zygentoma Ephemeroptera Insecta Odonata Plecoptera Embiodea Pterygota Zoraptera Dermaptera Grylloblattodea ? Mantophasmatodea Orthoptera Phasmatodea Blattaria Isoptera Mantodea Neoptera Psocoptera Phthiraptera Thysanoptera Hemiptera Coleoptera Rhaphidioptera Megaloptera Neuroptera Hymenoptera Holometabola Mecoptera Siphonaptera Diptera Strepsiptera Trichoptera Lepidoptera

Stages of Insect Evolution (Carpenter, 1953) 3. Wing Flexion Ephemeroptera 3. Development of wing flexion mechanisms Odonata Ephemeroptera + Odonata = Paleoptera

Stages of Insect Evolution (Carpenter, 1953) 3. Wing Flexion

Stages of Insect Evolution (Carpenter, 1953) 3. Wing Flexion Development of wing flexion mechanism 1. Neopterous condition 2. Allowed for better running locomotion, etc. 3. Became dominant and today represents 90% of orders and 97% of species 4. Includes all other modern insects

Stages of Insect Evolution (Carpenter, 1953) 4. Development of Metamorphosis Hemimetabolous (Incomplete metamorphosis) Holometabolous (Complete metamorphosis)

Stages of Insect Evolution (Carpenter, 1953) 4. Development of Metamorphosis

Imaginal Discs

Stages of Insect Evolution (Carpenter, 1953) 4. Development of Metamorphosis Hemimetabolous Holometabolous

Stages of Insect Evolution (Carpenter, 1953) 4. Development of Metamorphosis Evidence for pronymph as holometabolous larva - First instar cuticle in both secreted at same time - Lack wing buds - Similar reduced nervous systems - Both have high levels of JH

Hexapoda Insecta Pterygota Neoptera Holometabola Apterygotes 500 400 300 200 100 0 Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Entognatha Archaeognatha Hexapoda Zygentoma Ephemeroptera Insecta Odonata Plecoptera Embiodea Pterygota Zoraptera Dermaptera Grylloblattodea ? Mantophasmatodea Orthoptera Phasmatodea Blattaria Isoptera Mantodea Neoptera Psocoptera Phthiraptera Thysanoptera Hemiptera Coleoptera Rhaphidioptera Megaloptera Neuroptera Hymenoptera Holometabola Mecoptera Siphonaptera Diptera Apterygotes Strepsiptera Trichoptera Paleoptera Lepidoptera Hemimetabolous Holometabolous